actions/itgmania212121
1
0
Fork 0
Code Issues Pull Requests Actions 1 Packages Projects Releases Wiki Activity

worked on Error diffusion dithering algorithm, but it doesn't end up looking much better than OrderedDither

Browse Source
This commit is contained in:
Chris Danford
2003-04-05 21:17:51 +00:00
parent 2cc91afd04
commit 0bb7164b91
5 changed files with 118 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files
stepmania/src/RageBitmapTexture.cpp
+1
View File
@@ -352,6 +352,7 @@ retry:
PixFmtMasks[pixfmt].masks[2], PixFmtMasks[pixfmt].masks[3]);
SM_SDL_OrderedDither(img, dst);
//SM_SDL_ErrorDiffusionDither(img, dst);
SDL_FreeSurface(img);
img = dst;
}
stepmania/src/SDL_dither.cpp
+75
View File
@@ -6,6 +6,13 @@
#define DitherMatDim 4
/*
Added error-diffusion algorithm. (SM_SDL_ErrorDiffusionDither)
Error distributed per-row, left to right.
http://www.gamasutra.com/features/19990521/pixel_conversion_03.htm
*/
/* Fractions, 0/16 to 15/16: */
static const int DitherMat[DitherMatDim][DitherMatDim] =
{
@@ -122,3 +129,71 @@ void SM_SDL_OrderedDither(const SDL_Surface *src, SDL_Surface *dst)
}
}
}
#define CLAMP(x, l, h) {if (x > h) x = h; else if (x < l) x = l;}
void SM_SDL_ErrorDiffusionDither(const SDL_Surface *src, SDL_Surface *dst)
{
/* We can't dither to paletted surfaces. */
ASSERT(dst->format->BytesPerPixel > 1);
/* For each row: */
for(int row = 0; row < src->h; ++row)
{
Sint32 accumError[4] = { 0, 0, 0, 0 }; // accum error values are reset every row
const Uint8 *srcp = (const Uint8 *)src->pixels + row * src->pitch;
Uint8 *dstp = (Uint8 *)dst->pixels + row * dst->pitch;
/* For each pixel in row: */
for(int col = 0; col < src->w; ++col)
{
Uint8 originalColors[4];
mySDL_GetRGBAV(srcp, src, originalColors);
Uint8 colorsPlusError[4];
int c;
for(c = 0; c < 4; ++c)
{
// move some error to the new pixel (without overflowing)
Sint32 errorToAdd;
if( accumError[c] >= 0 )
errorToAdd = min( accumError[c], (Sint32)255 - originalColors[c] );
else
errorToAdd = max( accumError[c], (Sint32)-originalColors[c] );
colorsPlusError[c] = (Uint8)(originalColors[c] + errorToAdd);
accumError[c] -= errorToAdd;
// make sure we didn't overflow
ASSERT( (Uint8)(originalColors[c] + errorToAdd) == (Sint32)(originalColors[c] + errorToAdd) );
}
mySDL_SetRGBAV(dstp, dst, colorsPlusError);
Uint8 ditheredColors[4];
mySDL_GetRGBAV(dstp, dst, ditheredColors);
for(c = 0; c < 4; ++c)
accumError[c] += originalColors[c] - ditheredColors[c];
/* Blank the alpha accumulated error.
* This has the effect of not dithering the alpha channel. */
accumError[3] = 0;
for(c = 0; c < 4; ++c)
{
// Reduce funky streaks in low-bit channels by clamping error.
CLAMP( accumError[c], -128, +128 );
// Keep only a fraction of the error to make the effect more subtle.
accumError[c] /= 4;
}
srcp += src->format->BytesPerPixel;
dstp += dst->format->BytesPerPixel;
}
}
}
stepmania/src/SDL_dither.h
+1
View File
@@ -2,5 +2,6 @@
#define SM_SDL_DITHER_H 1
void SM_SDL_OrderedDither(const SDL_Surface *src, SDL_Surface *dst);
void SM_SDL_ErrorDiffusionDither(const SDL_Surface *src, SDL_Surface *dst);
#endif
stepmania/src/SDL_utils.cpp
+37
View File
@@ -107,6 +107,27 @@ void mySDL_GetRawRGBAV(const Uint8 *p, const SDL_Surface *src, Uint8 *v)
mySDL_GetRawRGBAV(pixel, src, v);
}
void mySDL_GetRGBAV(Uint32 pixel, const SDL_Surface *src, Uint8 *v)
{
mySDL_GetRawRGBAV(pixel, src, v);
const SDL_PixelFormat *fmt = src->format;
v[0] = v[0] << fmt->Rloss;
v[1] = v[1] << fmt->Gloss;
v[2] = v[2] << fmt->Bloss;
// Correct for surfaces that don't have an alpha channel.
if( fmt->Aloss == 8)
v[3] = 255;
else
v[3] = v[3] << fmt->Aloss;
}
void mySDL_GetRGBAV(const Uint8 *p, const SDL_Surface *src, Uint8 *v)
{
Uint32 pixel = decodepixel(p, src->format->BytesPerPixel);
mySDL_GetRGBAV(pixel, src, v);
}
/* Inverse of mySDL_GetRawRGBAV. */
Uint32 mySDL_SetRawRGBAV(const SDL_PixelFormat *fmt, const Uint8 *v)
{
@@ -122,6 +143,22 @@ void mySDL_SetRawRGBAV(Uint8 *p, const SDL_Surface *src, const Uint8 *v)
encodepixel(p, src->format->BytesPerPixel, pixel);
}
/* Inverse of mySDL_GetRGBAV. */
Uint32 mySDL_SetRGBAV(const SDL_PixelFormat *fmt, const Uint8 *v)
{
return (v[0] >> fmt->Rloss) << fmt->Rshift |
(v[1] >> fmt->Gloss) << fmt->Gshift |
(v[2] >> fmt->Bloss) << fmt->Bshift |
(v[3] >> fmt->Aloss) << fmt->Ashift;
}
void mySDL_SetRGBAV(Uint8 *p, const SDL_Surface *src, const Uint8 *v)
{
Uint32 pixel = mySDL_SetRGBAV(src->format, v);
encodepixel(p, src->format->BytesPerPixel, pixel);
}
/* Get the number of bits representing each color channel in fmt. */
void mySDL_GetBitsPerChannel(const SDL_PixelFormat *fmt, Uint32 bits[4])
{
stepmania/src/SDL_utils.h
+4
View File
@@ -14,9 +14,13 @@ void encodepixel(Uint8 *p, int bpp, Uint32 pixel);
void mySDL_GetRawRGBAV(Uint32 pixel, const SDL_Surface *src, Uint8 *v);
void mySDL_GetRawRGBAV(const Uint8 *p, const SDL_Surface *src, Uint8 *v);
void mySDL_GetRGBAV(Uint32 pixel, const SDL_Surface *src, Uint8 *v);
void mySDL_GetRGBAV(const Uint8 *p, const SDL_Surface *src, Uint8 *v);
Uint32 mySDL_SetRawRGBAV(const SDL_PixelFormat *fmt, const Uint8 *v);
void mySDL_SetRawRGBAV(Uint8 *p, const SDL_Surface *src, const Uint8 *v);
Uint32 mySDL_SetRGBAV(const SDL_PixelFormat *fmt, const Uint8 *v);
void mySDL_SetRGBAV(Uint8 *p, const SDL_Surface *src, const Uint8 *v);
void mySDL_GetBitsPerChannel(const SDL_PixelFormat *fmt, Uint32 bits[4]);
void ConvertSDLSurface(SDL_Surface *&image,